Much effort has been invested in techniques for accurately tracking and drilling boreholes in position relative to existing boreholes. Many such techniques rely on the conductivity or ferromagnetism of steel tubing in the reference borehole, yet such techniques are not applicable to open (uncased) boreholes, which may be where an intervention is most needed.
Before a borehole can be cased, it must be drilled. It is during the drilling process itself when the results of pressure differential, such as hydrocarbon kicks or blowouts, occur. In many cases, the pressure differential is so severe that the operator may drill a relief well. A relief well may intersect the initial borehole and be used in order to inject a dense “kill” fluid that suppresses further influx of formation fluid into the original borehole. Relief wells may intersect a target borehole below the differential influx depth, or at least as close to the deepest point of the borehole as practicable, but open boreholes cannot be located with existing techniques that rely on the material properties of casing.
It should be understood, however, that the specific embodiments given in the drawings and detailed description thereto do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.